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Benjamin Franklin and Electricity

Benjamin Franklin studied many different branches of science. He studied smoky chimneys; he invented

bifocal spectacles; he studied the effect of oil upon ruffled water; he identified the "dry bellyache" as

lead poisoning; he advocated ventilation in the days when windows were closed tight at night, and with

patients at all times; he investigated fertilizers in agriculture. His scientific observations show that he

foresaw some of the great developments of the nineteenth century.

His greatest fame as a scientist was the result of his discoveries in electricity. On a visit to Boston in 1746

he saw some electrical experiments and at once became deeply interested. A friend, Peter Collinson of

London, sent him some of the crude electrical apparatus of the day, which Franklin used, as well as

some equipment he had purchased in Boston. He wrote in a letter to Collinson: "For my own part, I

never was before engaged in any study that so engrossed my attention and my time as this has lately

done."

Georg Ohm

In two important papers in 1826, Ohm gave a mathematical description of conduction in circuits

modeled on Fourier's study of heat conduction. These papers continue Ohm's deduction of results fromexperimental evidence and, particularly in the second, he was able to propose laws which went a long

way to explaining results of others working on galvanic electricity.Ohm's Law

Using the results of his experiments, Georg Simon Ohm was able to define the fundamental relationship

between voltage, current, and resistance. What is now known as Ohm's law appeared in his most

famous work, a book published in 1827 that gave his complete theory ofelectricity.

The equation I = V/R is known as "Ohms Law". It states that the amount of steady current through a

material is directly proportional to the voltage across the material divided by the electrical resistance of

the material. The ohm (R), a unit of electrical resistance, is equal to that of a conductor in which a

current (I) of one ampere is produced by a potential of one volt (V) across its terminals. These

fundamental relationships represent the true beginning of electrical circuit analysis.

Current flows in an electric circuit in accordance with several definite laws. The basic law of current flow

is Ohm's law. Ohm's law states that the amount of current flowing in a circuit made up of only resistors

is related to the voltage on the circuit and the total resistance of the circuit. The law is usually expressed

by the formula V= IR (described in the above paragraph), where I is the current in amperes, V is voltage

(in volts), and R is the resistance in ohms.

Alessandro Volta and Electricty

Volta's most ground-breaking work was that lead to the development of the first battery. The roots of

this work can be traced back to some investigations performed by a fellow Italian and friend of Volta. He

discovered that when an electrical discharge occurred near a frog's leg whilst it was being dissected, the

discharge made its leg twitch. The Italian professor made many further researches and this lead to his

discovery that when two dissimilar metals were placed on the leg, and electric current was generated.

For many years it was believed that this was a new form of electricity that they called "animal

electricity".

Volta himself performed many experiments to investigate the phenomenon further. He even started to

place dissimilar metals on his tongue and close to his eye with various effects. However as he undertook

further experiments he became more convinced that the electricity was being generated by the two

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dissimilar metals separated by a solution such as brine. Galvani, though continued to defend his idea of

animal electricity.

Research of Charles-Augustin de Coulomb

In 1785, Coulomb presented his three reports on Electricity and Magnetism:- Premier Mmoire sur

llectricit et le Magntisme.[2]In this publication, Coulomb describes "How to construct and use anelectric balance (torsion balance) based on the property of the metal wires of having a reaction torsion

force proportional to the torsion angle." Coulomb also experimentally determined the law that explains

how "two bodies electrified of the same kind of Electricity exert on each other." On page 574 he states:

Il rsulte donc de ces trois essais, que l'action rpulsive que les deux balles lectrifes de la mme nature

d'lectricit exercent l'une sur l'autre, suit la raison inverse du carr des distances.

Translation: It follows therefore from these three tests, that the repulsive force that the two balls --

[which were] electrified with the same kind of electricity -- exert on each other, follows the inverse

proportion of the square of the distance.

- Second Mmoire sur llectricit et le Magntisme.[3]In this publication, Coulomb carries out the"determination according to which laws both the Magnetic and the Electric fluids act, either by repulsion

or by attraction." On page 579, he states that the attractive force between two oppositely charged

spheres is proportional to the product of the quantities of charge on the spheres and is inversely

proportional to the square of the distance between the spheres.

- Troisime Mmoire sur llectricit et le Magntisme.[4]"On the quantity of Electricity that an isolatedbody loses in a certain time period, either by contact with less humid air or in the supports more or less

idio-electric."

Four subsequent reports were published in the following years:

- Quatrime Mmoire[5]

"Where two principal properties of the electric fluid are demonstrated: first,

that this fluid does not expand into any object according to a chemical affinity or by an elective

attraction, but that it divides itself between different objects brought into contact; second, that in

conducting objects, the fluid, having achieved a state of stability, expands on the surface of the body

and does not penetrate into the interior." (1786)

- Cinquime Mmoire[6]

"On the manner in which the electric fluid divides itself between conducting

objects brought into contact and the distribution of this fluid on the different parts of the surface of this

object." (1787)

- Sixime Mmoire

[7]

"Continuation of research into the distribution of the electric fluid between severalconductors. Determination of electric density at different points on the surface of these bodies." (1788)

- Septime Mmoire[8]

"On magnetism" (1789)

Coulomb explained the laws of attraction and repulsion between electric charges and magnetic poles,

although he did not find anyrelationshipbetween the two phenomena. He thought that the attraction

and repulsion were due to different kinds offluids.

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